Nicholas J. Cotsonika’s weekly Three Periods column appears on Thursdays. This week’s topics include Torey Krug’s rookie breakout for the structured Bruins; more former players joining the brain-trauma lawsuit against the NHL; how Jonathan Ericsson went from last in the draft to a “lifetime” deal with Detroit; what Clarke MacArthur, Kyle Turris and Bobby Ryan have in common as they click for the Senators; plus notes on the Ducks, Blues, Penguins and more.

FIRST PERIOD: Why is little Torey Krug scoring big for the Bruins?

Torey Krug is 22. He is 5-foot-9. He has played only 43 NHL games – 28 in the regular season, 15 in the playoffs. So how has he become an offensive dynamo on the blue line for a team known for its experience, toughness and structure?

Talent, of course. Confidence, of course. But it’s coaching and context, too.

Coach Claude Julien has gone through guys like Derek Morris, Dennis Wideman and Tomas Kaberle, but he hasn’t had a guy quite like Krug. The kid scored four goals in the playoffs last season, all in a five-game second-round series against the New York Rangers, when he got a chance to play because of injuries. He has seven goals this season, tied for the lead among NHL defensemen with the likes of Erik Karlsson and Shea Weber.

“We’ve lacked that for a long time,” Julien said.

Julien has put Krug in positions to succeed – third-pair minutes at even strength, point on the power play – and he can protect him because he has, say, 6-foot-9 Norris Trophy winner Zdeno Chara.

“I would do it, too, if I was coaching this team,” Krug said. “Sometimes, third period, faceoff in our ‘D’ zone, we’re going to put out someone else that’s a little bit bigger than me. They’re going to get the puck out, and then we’re going to change.”

At the same time, Julien has given Krug a chance to do his thing. The coaches talk to Krug about when to jump into the play and when not to, when to take risk, when to avoid it. But they don’t tell him not to jump into the play, not to take risk.

“At one point as a coach, you’ve also got to allow a player to play within his strength,” Julien said. “We don’t hold people back, we hold people accountable. It’s for him to get better at finding the right times to go and when to stay back and not take that chance, and that comes with experience. I think you’ve got to give him that opportunity.”

“He’s going to learn from his mistakes, and we know he’s going to make mistakes. But right now, he’s just bringing too much positive to the table to say, ‘You know, you can’t do this anymore.’ ”

Krug said he is at his best when he is in shoot-first, attack mode. But he does not want to be known as an offensive defenseman. He feels he is earning the coaches’ trust and getting more opportunities in defensive situations, too.

“They do get a little bit upset if I’m not as efficient as I should be and I’m trying to make silly plays,” Krug said. “So for me, it’s just all about being efficient, making sure I’m not putting myself in battles I can’t win physically, and it’s something that we talk about on a daily basis.”

SECOND PERIOD: More players joining brain trauma lawsuit against NHL

It began with 10 plaintiffs – 10 men who had played in the NHL, suffered brain trauma and experienced symptoms that could be related. But more than 200 players already have joined the class-action lawsuit against the league since it was filed Monday, and no doubt there will be more. There may be more lawsuits, too.

This suit alleges the NHL knew or should have known the risks of brain trauma, promoted and profited from on-ice violence, did too little too late to address the problem, and caused harm to the players. It seeks to represent all former NHL players who retired on or before Feb. 14, 2013, and suffered brain trauma, and it seeks medical monitoring and “the full measure of damages allowed under applicable law.” It follows a class-action suit against the NFL that netted a $765 million settlement.

The lawyers have been recruiting former players, even in public on Twitter. Check the feed of Mel Owens (@MelOwens58), and you see him tweeting the news of the lawsuit to guy after guy. Bob Bourne, who played 14 seasons in the NHL and won four Stanley Cups with the New York Islanders, said he was approached two or three weeks ago and decided to join the suit this week. He tweeted his own news to members of the media Wednesday and made himself available for interviews across North America.

“I’m reluctant,” Bourne told Yahoo Sports. “The NHL has been good to me.”

So why join the suit? For money? For answers – what did the NHL know, when did it know it, why didn’t it do more?

What did he want to say to the media?

“I guess I just want to say it’s got nothing to do with trying to get money,” Bourne said. “I don’t think there’d be that much money, anyway. But I need to find out about my health. I’m no different than any other human being. I want to know what my health is going to be like.”

Bourne said he never had a concussion officially, but “we didn’t know then” and he suffered all kinds of brain trauma – nine or 10 broken noses, a face smashed into the dasher, fights, et cetera. Now 59, he said he is not suffering from major symptoms, “nothing different than the general population,” and “this is not woe-is-me.” That said, he said he has gone through about five jobs, not counting hockey. He has trouble concentrating at times. “I know there has been some kind of damage,” he said.

Bourne said he had seen a doctor. Asked why he would sue the NHL to find out about his health, he said it was “hard to explain.” He expects others to follow. Each will have his own story and motivation.

“What happened, happened,” Bourne said. “If there’s something that can come out that’s beneficial, that’s great. You know, life after hockey hasn’t been fun, and it hasn’t been fun for a lot of guys.”

THIRD PERIOD: Ericsson goes from last in draft to “lifetime” deal

In 2002, Jonathan Ericsson was the last pick in the NHL draft (291st overall). If this were the NFL, he would have been known as Mr. Irrelevant.

“I think they called me that a lot of times,” Ericsson said.

He laughed. He can laugh now. On Wednesday, he signed a six-year, $25.5 million contract extension with the team that drafted him, the Detroit Red Wings. Coach Mike Babcock called it a “lifetime” deal.

This was sooooo Wings. This is the team that drafted Tomas Holmstrom in the 10th round (257th overall) in 1994, Pavel Datsyuk in the sixth round (171st overall) in 1998 and Henrik Zetterberg in the seventh round (210th overall) in 1999. Ericsson isn’t in Holmstrom’s class, let alone in Datsyuk’s or Zetterberg’s. But he is another product of the Wings’ director of European scouting, Hakan Andersson, and he is another product of the Wings’ program.

The Wings haven’t had high draft picks over the years because they have won and made trades trying to win, so they have had to find gems late in the draft. Patience has been a necessity and a luxury – a necessity because they have had to let their prospects develop, a luxury because they have had a good enough team to give them time to do it.

“The formula for us, I guess, is we hold on to some older players longer because we don’t have those blue-chip kids coming on to our team,” said general manager Ken Holland. “We think we’ve got kids that we can develop into NHL players, so patience has to be part of our program. Fortunately in this situation, it’s probably worked out good.”

The Wings kept Ericsson in Sweden until 2006. They kept him in the minors for the most part until 2009. They kept him low on the depth chart when he made the NHL full-time, behind players like Nicklas Lidstrom, Brian Rafalski and Brad Stuart. They stuck with him when he made mistakes and the fans howled, because he was 6-foot-5 and mobile and still learning. Now Lidstrom, Rafalski and Stuart are gone, and he’s on the top pair and a key penalty-killer at age 29.

Some outside the Wings organization think he’s slotted too high; Holland says he’s a solid No. 2 or No. 3. But there is no question he would have been in demand as an unrestricted free agent because the market is so thin for defensemen, and he came so far in Detroit that he wanted to stay.

“I think I’ve always been a late bloomer when it comes to kind of everything,” said Ericsson, whose brother, Jimmie, plays in the Swedish Elite League. “I haven’t always been the most talented guy. My older brother is more talented than me hockey-wise, but he hasn’t liked working out and being that determined to maybe reach that far. He’s a great hockey player, but he doesn’t have that mentality maybe off the ice that maybe I have.”

OVERTIME: Good timing for MacArthur, Turris, Ryan and the Senators

The Ottawa Senators have had their issues – penalties, defense, consistency. But there has been a bright spot: The line of Clarke MacArthur, Kyle Turris and Bobby Ryan.

Each player came from elsewhere – MacArthur from Toronto, Turris from Phoenix, Ryan from Anaheim. Each came differently – MacArthur as a free agent in July, Turris after forcing a trade in 2011-12, Ryan after hearing lots of rumors and finally being dealt in July. But they had something in common: the desire to play a greater role.

“I think all of us wanted to be put in that position,” said Ryan, who scored more than 30 goals four times with the Ducks but still was the third wheel to Ryan Getzlaf and Corey Perry (and wasn’t as big a star as Teemu Selanne, either). “We’ve been able to step to the front of the line.”

MacArthur and Turris were together from the first day of training camp. Ryan joined them early in the season and clicked immediately. Now they are a good combination – MacArthur bringing quickness and finesse, Turris a two-way game, Ryan size and scoring touch.

All three have produced at even strength and on the power play. Ryan leads the team in goals (13) and is second in points (24). Turris has six goals and 21 points. MacArthur has six goals and 18 points. The trio is a combined plus-28.

“I think a lot of times for a player, change is good,” said Sens coach Paul MacLean. “Now that they’ve come here, they’re ready to be players, and we have the opportunity to allow them to be players. I think the situation – the timing of their careers – for all of them has been good.”

SHOOTOUT: Notes from around the NHL

— Getzlaf became captain of the Ducks in 2010-11. He produced that season with 76 points in 67 games. He struggled in 2011-12 with 57 in 67. But he rebounded with 49 in 44 last season and has 28 in 24 this season, near the top of the NHL in scoring. “When you make a guy like Getzy captain, sometimes there’s a transition period,” said Ducks GM Bob Murray. “Sometimes Getzy thinks too much, and I think Getzy’s over that now. Everything’s not a huge problem anymore. He just plays.”

— The Bruins got a rare look at the St. Louis Blues last week, and what did they see in a 3-2 shootout loss? “They’re patient defensively,” said Bruins defenseman Johnny Boychuk. “They just wait for you to make a mistake, and they capitalize on it.” Asked if they reminded him of anyone, Boychuk said: “Us?” Exactly. “They have the potential to be champions,” he said. “They’ve got a good formula over there. Maybe we’ll meet them.”

— Martin Erat asked the Nashville Predators to trade him, and he agreed to be shipped to the Washington Capitals. Now he has asked the Caps to trade him. He has zero goals and a $4.5 million cap hit, though his salary is actually $3.75 million this season and $2.25 million next season. Who has the cap space and the willingness to add a potential headache?

— Watch Matt Niskanen while Paul Martin recovers from his broken leg. Niskanen has been an effective defenseman when slotted properly for the Pittsburgh Penguins, but he has had a harder time when asked to play a larger role.

— Can’t take credit for this one, but in the Detroit press box Wednesday night, the line of Dan Cleary, Stephen Weiss and Mikael Samuelsson was dubbed the No-Production line. The Red Wings have lacked secondary scoring, and Cleary ($1.75 million cap hit this season), Weiss ($4.9 million cap hit for five seasons) and Samuelsson ($3 million hit this season) have combined for four goals and four assists in 91 games. Gordie Howe, Sid Abel and Ted Lindsay they are not.

— John Tortorella returns to New York on Saturday. Daniel Alfredsson returns to Ottawa on Sunday. Both should be received well, especially Alfredsson. Tortorella was fired because he wore out the Rangers, but he squeezed as much out of them as he could, taking them all the way to the Eastern Conference final in 2012. Alfredsson left as a free agent in an awkward dispute over money, but he is an Ottawa icon and led the Senators to the Cup final in 2007.